Recording and reproducing sound



v June 15, 1937'. w M. BENDER 2,083,815 nncoanme AND REPRODUCII IG sobm':

- Filed 001;. 12, 1931 Ml a wlzz 6" W 3 'IYNVENTOR l,

. I Max Bender ATTORNEY Patented June 15, 1937 v UNITED STATES PATENT orrics nEconnING AND nnrnopocme sown Max Bender, New York, N. Y., assignor, by meme assignments, to United Acoustlgraph Corporation, a corporation of Nevada Application October 12, 1931, Serial No. 588,331!

7 Claims.

This invention relates to recording and reproducing of sound and has for its principal object an improved method and apparatus for recording sound in the form of a groove on relatively hard material such as a film of celluloid or similar material.

In my co-pending application Serial Number 539,103, filed May 21, 1931, I disclose a method and apparatus for recording sound in the form 10 of a hill and dale groove wherein the styluses employed are of such form and so positioned with respect to the film as to permit accurate record over a wide range of frequencies.

The present invention constitutes an improvement in the form or angulation of the cutting stylus.- As disclosed in my co-pending application the cutting stylus has an edge extending in a general direction normal to the direction of movement of the film. In the present form of my invention the cuttingedge of the stylus as it meets the film is for the most part inclined to the normal so that the cutting operation is somewhat similar to the action of a plow which cuts afurrow by an edge which is inclined both to the direction of movement and also to a plane ting stylus engaging a film, the view being taken in the direction of movement of the film and the cutting stylus being shown in elevation and the film in section;

Figure 2 is a side elevation partly in section of the structure shown in Figure 1 showing the film as it is drawn over an. anvil of relatively small diameter;

Figure 3 is a top plan view of the-structure shown in Figure 1;

Figure 4 is a view similar to Figure 1 but showing a modified form of stylus, this stylus being positioned with its axis inclined to a vertical plane .50 passing through the longitudinal axis of the I of the structure shown in Figure 4;

.55'shown in Figure 4; and

Figure 6 is a top plan view of the structure Figure '7 is a fragmentary view showing a means for holding and vibrating the stylus.

It will be understood that the styluses disclosed will normally be operated by electromagnetic devices such as that shown in my co-pending application althoughv iii-certain cases they may be operated by diaphragms. The cutting point of the stylus is moved upward and downward in accordance with the sound vibrations and serves to cut a hill and dale groove in the film to. In practice, suitable means will be employed for compensating for the dififerences in force required to press the cutting edge into the film and that required to move it out. This compensating means may take the form of an eccentric positioning of the armature with respect to the magnetic poles or a difference in the elastic and frictional damping such as disclosed and claimed in the patent of Earl H. Foley, No. 1,870,446, the purpose being to produce a sound groove of regular or substantial form.

The anvil I3 which is preferably formed of metal such as steel has a smooth upper guiding surface for the film. The drive for the film may be frictional or by means of a sprocket engaging 'the usual side openings in the film. The film is fed against the cutting edge of the stylus under considerable tension and it will be noticed, for example, from Figure 2 that the film it as it passes the stylus is moved over an arc Hit of relatively short radius as for example 34; inch in radius which is one of the important features of the inventiondisclosed in my co-pending application.

Figures 1 to 3, I show on an enlarged scale one form" of stylus in contact with a moving film.

This stylus has a lower conical side 22 and an upper side 23 which'as shown is elliptical in form and which meets the lower side ina curved cutting edge 2'5 which should be formed as sharp as possible. .The angle 0 between the longitudinal axis of the side 23 and the element of the conical surface 22 which meets the side 23 is substantially There should be a clearance angle angle A of say between 17 and 25 between the normal to the film at the cutting point and the side 23.

It will be seen particularly from Figure 3 that the cutting edge does not extend directly across the sound groove but is inclined thereto, thus cutting the material of the film by a slicing action which greatly improves the character or the cut.

I find that by placing the cutting-stylus with the longitudinal axis of the stylus and also the longitudinal axis of the side 23 in a vertical plane passing through the axis of the groove at the angle to the film-before mentionedand then turning the stylus on its own axis say 15 to 25, I secure the desired inclination of the cutting edge to the axis of the groove. As in the case of the stylus disclosed in my co-pending application the material of the film cut away is in the form of a continuous core of exactly the form of the groove.

In Figures 4, 5 and 6, 1 show a modified form of stylus of cylindrical shape with an inclined end hollowed out to form an upper cutting surface 30. The angle between the plane of the outer edge of this surface and the lower face 34 of the cylinder, that is, between this plane and any element of the cylinder may be as great as 70 and it is understood that generally by this structure I am able to reduce the cutting angle, that is, the angle between the cutting face 30 and the lower surface 3| which in the form illustrated is approximately 45. It will be seen that there is. a relatively large clearance angle between the lower face of the stylus and the film and it will also be seen from Figure 6 that the axis of the cutting stylus is inclined to a vertical plane passing through the axis of the groove and that the cutting edge is also inclined across the groove as in the case of the stylus shown in Figures 1 to 3. The groove cut by the styluses will be elliptical or approximately cylindrical in section. It is obvious that by properly designing the stylus the angles above noted may be maintained at substantially the proper values, and the groove cut by them at any given depth, be substantially cylindrical.

In reproducing, I preferably employ a pick-up stylus constructed as disclosed in my co-pendlng application, the lower surface of the stylus being curved to contact along the width of the groove, this pick-up stylus being turned slightly on its own axis so that its lower edge is inclined to a plane normal to the axis of the groove. By the use of the invention herein described, I have been able to record on a film moving at the rate of 60 feet a minute, sound vibrations within an audible range up to a frequency in excess of fivethousand and to reproduce without appreciable distortion and perceptible surface sound and by recording and reproducing at a film speed of 90 feet a minute I am able to increase the upper frequency range 50% that is to a frequency of seven thousand five hundred.

In practice I preferably employ a light out of approximately 1.5 mils.

In Figure '7, I show one means for holding the cutting and reproducing styluses. Lever G0 is.

designed to be actuated by an electromagnet (not shown) and carries a clamping device 65 for holdinglthe stylus at the proper angle. In Figure 7 I show at the right a cutting stylus which may be of any of the forms illustrated in the previous figures, and at the left I show a reproducing stylus designed to operate in the groove formed by the cutting stylus. In changing from the cutting to the reproducing operation, either the anvil l3 or the recorder head will be shifted so that the reproducing stylus will operate in the sound groove. I claim: J h

1. A method of progressively cutting a hill and dale sound record groove in tough plasticized film by means of a tool formed with two surfaces meeting at an angle of from 45 to 60 to form a cutting edge, which method consists in drawing said film against said edge under considerable tension at a speed substantially in excess of '40 feet per minute, holding the tool with said edge inclined, transversely of the groove, to a plane dale sound record groove in a thin, flexible film of tough plasticized material by means of a cutting tool having a sharp cutting edge, which method consists in drawing the film over an anvil having a sharp bend, holding the tool to cut the film at the point where the film passes over the bend and with the cutting edge at a general incline, transversely of the groove, to a plane normal to the axis of the groove to be cut and causingthe tool to vibrate substantially normal to the film in accordance with sound waves to be recorded.

3. A method of progressively cutting a hill and dale sound record groove in tough plasticized material by means of a tool formed with two surfaces meeting at an angle of from 45 to 60 to form a cutting edge, which method consists in drawing said film over an anvil having a sharp bend, holding said tool with its cutting edge at said bend and inclined, transversely of the groove, to a plane normal to the direction of movement to said film and one of said faces adjacent said film at an angle in excess of 7 thereto and another of said faces at an angle of more than 17 from the normal to said film at the edge, said angle being measured in the direction of motion of the film and vibrating the tool in a direction substantially normal to the film.

4. Means for cutting a sound record groove in a thin tough film comprising a cutting tool having surfaces meeting to form asharp curved cutting edge, an anvil for supporting the'film, means for drawing the film over said anvil and against said cutting edge, means for supporting said tool with the surfaces extending away from the edge in the direction of movement of the material, with the edge extending transversely of the groove and with the edge curve components, transverse of the groove, lying at a general incline to the normal to the axis of the. groove so as to effect a slicing action of the film and means for vibrating the tool in accordance with sound waves to be recorded.

5. A method of progressively cutting a sound record groove in tough plasticized sheet by means of a tool formed with two surfaces meeting at an angle of from 45 to 60 to. form a cutting edge, which method consists in drawing said sheet against said edge, holding the tool with the tool penetrating the sheet and the edge inclined, transversely of the groove, to a plane normal to the direction of movement of the sheet and with one of said faces adjacent the accordance with the sound to be recorded.

6. The method of cutting a record groove in a sheet of tough plasticized material by means of a cutting tool having a sharp cutting edge, which method consists in drawing said material against e,,s1o 3 direction of movementv oi the sheet, whereby a slicing action is eftected and vibrating the tool in accordance with sound to be recorded.

7. The method of cutting a hill and dale rec- I ord groove in tough plasticized film by means'of a cutting tool having a 'sharpoutting edge, which 1 method consists in drawing "said film against said edge. holding the tool with the edge penetrating the film and the edge inclined, transversely of the groove, to-a plane normal to the direction of movement of the fllm,.whereby a; slicing action is effected and vibrating the tool in accordance with sound to be recorded. and in a direction normal to the film surface. 7

'MAX BENDER. 

